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H. GARMIOHAEL. METHOD OF AND APPARATUS FOR BLEGTROGHEMIGAL DECOMPOSITION.

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METHOD OF AND APPARATUS FOR ELECTROCHEMICAL DEGOMPOSITION.

No. 518,710. A I A Patented Apr. 24, 1894.

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METHODOF AND APPARATUS FOR ELECTROCHEMICAL DECOMPOSITION.

SPECIFICATION forming part of Letters Patent No. 518,710, dated April 24, 1894. Application filed January 23, 1892. Eserial No. 419,068. (No model.)

To ttZZ whom, it may concern:

Be it known that I, HENRY CARMIOHAEL, of Malden, in the county of Middlesex, State of Massachusetts, have invented an Improvement in Methods of and Apparatus for Electrochemical Decomposition, of which the following description, in connection with the accompanying drawings, is a specification, like letters and figures 011 the drawings representing like parts.

The object of my invention is to render electro-chemical processes in general more productive and commercially more valuable than they have been heretofore.

The more particular aim of my invention is the provision of economical means for electrolyzing aqueous solutions of various chlorides, notably the solution of common salt.

Hitherto, methods of and apparatus for electrolysis of chlorides have been of little more than scientific interest, and of scarcely any commercial value, so far as known. to me. The contrivers of methods and apparatus for this purpose have been to a great extent baffled by the obstacles opposed by the chemical peculiarities of the substances resulting from the electrolysis; to separate the elements of a solution by electro-chemical means is not difficult, but to manage the elements separated has been and is a matter of so great difliculty that none of the methods used heretofore can be called commercially successful. A typical illustration of the behavior of the ions or products of electrolysis of chlorides is afforded by the process of separation of the elements in a solution of common salt by means of an electric current. Represented by chemical sysmbols the Well known electrochemical separation is this.

The sodium liberated at one electrode immediately decomposes the water of solution, forming the hydrate, or caustic soda;

the only substance apparent at the cathode, if we disregard hydrogen.

(I am aware that in many electrolyses the true ion, or liberated element, does not preserve its chemical integrity, but re-combines with substances in solution. For convenience, however, I desire to use the Word ion to mean whatever substance is sensibly present at either electrode, whether it be the elementary ion as usually understood, or a secondary combination of the elementary ion.) The ions are liberated apart upon the electrode surfaces but being soluble and diffusive they are soon brought together in the aqueous electrolyte between the poles Where they enter into chemical combination. The fluid currents engenderedby the escaping gases actively assist the mingling and combination of the electrolytic products. Sodium hydrate and chlorine form either sodium hypo chlorite, chlorite or chlorate according to temperature and other conditions. These uniting with hydrogen at the cathodes are resolved into chloride'of sodium and water which is the very solution originally decomposed. At the outset then necessity arises to keep the ions separate and to overcome or check diltusion and circulation whereby they are intermingled and recombined to form the original electrolyte. To accomplish this object has been the aim of various methods of electrolysis. These may be divided conveniently into two classes:-one wherein the means for separating the ions is mechanical; the other wherein chemical means are employed.

In most of the mechanical methods a diaphragm has been interposed between the electrodes to prevent the passage and intermingling of the ions. Such a diaphragm should be porous umn of electrolyte stands between the electrodes, and further should be of such dimensions and substance as to offer the least possible resistance to the passage of an electric current. Chemical methods of separation have employed some substance for which one of the ions has strong chemical aflinity. This substance placed at the electrode where the ion to be secured is delivered arrests the ion by forming a new compound with it as fast as it appears at the electrode. In addition so that an unbroken col- IOO to the expense and complication of such a process if the ion itself is the product desired, such a chemical method while removing one difficulty creates another, for the combination of the ion with the chemical arrester must be redecomposed by a subsequent auxiliary process.

The object of this invention is to render the mechanical separation of ions feasible and consistent with economical production.

Mechanical separators have been unsuccessful commercially for this reason among I others; because the ions in solution have not been obtained in a concentrated state without great waste of electric current. If the electrolyte is common salt and the desired ion caustic soda, as soon as the caustic soda becomes concentrated at the cathode its dif fusive tendency increasing proportionately causes it to pass through the electrolyte in spite of the interposition of a porous diaphragm, until it reunites with the chlorine set free at the anode. Moreover all the porous diaphragms hitherto employed have proved short-lived, because unable to resist the continued action of caustic soda; an apparatus employing such a destructible diaphragm is expensive to maintain and unreliable in use.

Again, the anodes proposed for the purpose have not been such as answer the requirements of practical manufacture.

By the process and apparatus of my invention herein described the obstacles above mentioned are overcome so far as to enable the manufacturing chemist to obtain the products of electrolysis in the state in which they are liberated at the electrode so that no further chemical process is necessary, and so that the ions are delivered continuously from the electrolytic cell in concentration sufficient for industrial purposes and with an efficiency of electric current very near the theoretical. By decomposing a strong solution of common salt by this method there can be obtained caustic soda in solutions containing from two hundred and fifty to three hundred and fifty grams or more of caustic soda to the liter, chlorine in equivalent quantities, and hydrogen as a by-product, with an efficiency of electric current of ninety per cent. and upward.

Following is a description of the method and apparatus which are my invention, as applied, first: to the electrolysis of solution of sodium chloride; second to the electrolysis of sodium sulphate; but I wish it to be understood that my method and apparatus are adapted to the electrolysis of any available solution.

In the accompanying drawings which form part of this specification Figure 1, is a vertical longitudinal section of an electrolytic cell suitable for commercial production of caustic soda, chlorine and hydrogen. Fig. 2 is an end sectional and perspective view of the apparatus shown in Fig. 1. Fig. 2 is an end sectional view of the apparatus of Figs. 1 and 2, showingon alarger scale the structure and arrangement of the containing-cell and diaphragm. Fig. 3, shows in section and perspective an insulated leading wire which is a detail of the apparatus. Fig. 4, shows in vertical section a cylindrical form of apparatus. Fig. 4. shows on a larger scale a section of part of the apparatus of Fig. 4. Fig. 5, is a horizontal section of the apparatus shown in Fig. 4 on the line 3, 4. Fig. 6, shows the cellular base of the apparatus of Figs. 4 and 5, in perspective. Figs. 7, 8, and 9, show details of the apparatus of Figs. 4 and 5. Fig. 8 is a section of part of the apparatus of Fig. 5, at the line y. Fig. 10, represents a battery of electrolytic cells, arranged in electric series,

together with auxiliary apparatus. Fig. 11, shows in vertical section a small apparatus for the electrolysis of sodium sulphate. Fig. 12 shows the bell jar and base of an apparatus similar to that shown in Fig. 4, with the bell jar surrounded by a belt of lagging, 8, and having its base-cathode corrugated on the outside, as at, 9.

Figs. 1 and 2 show a rectangular form of my electrolytic cell, consisting of a box of glass, slate or other suitable non-corrodible material. The box is double and is composed of an upper and a lower portion designated respectively U and L in Figs. 1 and 2. In the compartments U and L of the apparatus is placed the liquid to be electrol-yzed. The compartments U and L are separated by a diaphragm D, which is inclined to the horizontal. In Fig. 2 the diaphragm D is shown inclined in two directions like an inverted house roof. This diaphragm, and its counterpart in all apparatus used in connection with my process, is, generally speaking, con cavo-convex. Concavo-convex as understood by me and applied to. this description of my invention, does not involve a spherical surface merely, but defines broadly the construction of a diaphragm which may be pyramidal, or prismatic, as in Fig. 2, or conical, as in Figs. 4 and 11, or which might be arranged in a very large apparatus as a series of prismatic folds, forming a number of corrugations. This diaphragm should be of a porous inert material and should be made as thin as is consistent with necessary strength. In each of the compartments U and L is situated one of the electrodes of the cell, the anode in the compartment U, the cathode in the compartment L. Platinum is the best material for the anode, butif the high cost of platinum is an obstacle to its use, ga'searbon or some mineral conductor may be employed with a few leading wires of platinum. The anode of Figs. 1, 4, 5 and 11, is shown composed of lumps of gas carbon G, which rest on platinum wires W, which connect with the leading wires. The cathode is of iron, made preferably in such form as to serve for the base of the compartment L. The cathode base is shown at B in the figures; its electric connection is at X. The inner surface of the kathode base B is preferably inclined to the horizontal and corrugated so that the gases of decomposition may escape readily and not polarize the cathode. The walls u of the compartment U (which in Figs. 1 and 2, is smaller in horizontal area than compartment L) extend down into the compartment L as shown in Figs. 1 and 2. The surrounding walls lot the compartment L are surmounted by a cover 0, which closes the compartment L by form ing tight connections on all sides with the walls land a. The walls Z and 'u, and the cover inclose a space or chamber H whose function will be described presently. The outer edges of the diaphragm D are secured on all sides to the lower edges of the walls a in such manner as to form a tight joint.

The electrolytic cell is restricted in but one dimension, that is, its height. To remove the electrodes too far from one another would result in decrease of efficiency in the apparatus by reason of the consequent increase in the internal resistance of the cell. In operating with an apparatus similar in construction with that shown in Figs. 1 and 2 it has been found desirable to support the anode about two and one-half inches above the diaphragm and to bring the cathode as near the lower above the anode.

surface of the diaphragm as possible- This space of two and one-half or three inches appears to be ample for the isolation of the ions under the conditions of use and arrangement of cell as here set forth. If, however, it is desired to obtain ions in an extraordinarily high state of concentration at the expense of electrical energy, this distance between electrodes may be increased to suit the operator.

The electrolytic cell is filled with strong solution of common salt to a levelabout an inch The electric current is turned on and the familiar decomposition begins. At the anode G, chlorine is disengaged from the solution and rises to the top of the compartment U. Some of the chlorine is retained in solution in the electrolyte. At the cathode in the compartment L under the diaphragm D, sodium hydrate is formed and hydrogen is liberated. The diaphragm D prevents the hydrogen from rising through the electrolyte to the chlorine region. By its inclination the diaphragm D guides the liberated hydrogen into the chamber I-I, whence it escapes through a tube It to a suitable receiver. The hydrogen is delivered at h under such pressure as is necessary to keep the level of the liquid in the chamber H from rising to the tube It. The interposition of the diaphragm D between the compartments U and L serves two purposes: First. The hydrogen is not allowed to mingle with chlorine at the top of the cell and thus form an explosive mixture; and,second,the ebnllition of hydrogen is prevented from carrying the sodium hydrate into the presence of chlorine.

As described so far the electrolysis in this apparatus has not differed in method from that of known apparatus.

many days.

It is not in the formation of the ions that this process differs from others, but inthe subsequent mode of disposing of the ions so as to obtain them in the condition in which they have been developed at the electrodes, without interrupting the process of electrolysis. Nor is this the first electrolytic apparatus wherein a diaphragm has been employed. But the electrolytic cells known heretofore have employed diaphragms only to interrupt the flow of gases of electrolysis and by that means to prevent stirring by ebullition.

The diaphragm used in the apparatus described differs radically in structure from those used heretofore and combines the requisites of porosity, conductivity and strength.

A diaphragm which shall combine the above three requisites and also possess the ability to resist the action of caustic soda is constructed as follows: A cement-like silicate, as for instance hydraulic cement, is molded to the form desired for a diaphragm. To give the silicious sheet sufiicient flexibility and strength, it may be enforced with fibers or a textile fabric of suitable form and strength.

Asbestus fiber or asbestos cloth is preferred for the purpose, as being unaffected by the action of caustic soda. It is not absolutely necessary to use a resistant fiber, as the surrounding silicate protects the fiber from chemical actions until the silicate itself which forms an insoluble double silicate becomes so hard as to require no support.

An easy method of constructing a diaphragm is to fill the meshes of a sheet of as bestus cloth with the silicate, and mold this cloth to the form desired. Continued use has proved that a diaphragm of this construction is perfectly porous, interposes no appreciable resistance, and under ordinary working circumstances is indestructible.

As the solution of caustic soda in the compartment L increases in strength with each increment from the cathode it slowly diffuses up through the diaphragm D, and if allowed to accumulate indefinitely would ultimately join the chlorine at the anode. Thus, after the apparatus has been in operation a short time there are formed several horizontal zones of various compositions and density. At the top of the compartment U free chlorine collects in the space 0 L, whence it may be drawn through the pipe 0 Z. The electrolyte in the compartment Udivides itself into three horizontal zones. The uppermost zone Z lies just above the anode and with chlorine in solution. This zone Z be known as the chlorine zone.

Chlorine gas does not readily enter into solution in salt water especially if the solution is warm. Observation of the apparatus described has shown that the chlorine in the zone Zhas no sensible tendency to diffuse downward through the electrolyte even though the process be continued uninterruptedly for No precaution, therefore, need may is charged be taken against the downward travel of chlorine. If the upward diffusive movement of caustic soda is prevented or counteracted the object of keeping the ions asunder will be accomplished. Below the anode is the zone Z filled with a solution of common salt untinged by chlorine and free from diffusing caustic soda. This zone may be referred to as the chloride or electrolyte zone. Below the zone Z is the zone Z occupied by diffused caustic soda and electrolyte which as the concentration below the diaphragm D increases spreads up Ward toward the zone Z In an apparatus operating under ordinarily good conditions these zones are clearly defined to the eye. The chlorine zone at and above the anode is colored greenish yellow; the chloride zone is clear, and the diffused soda zone is clouded, on account of the presence of lime and magnesia as slight impurities in the electrolyte which are precipitated by the alkalir Below the diaphragm D is the region within the compartment L, marked NA, filled with concentrated caustic soda which slowly but constantly diffuses through the diaphragm to the diffused soda zone Z It has been intimated already that chlorine has but little tendency to diffuse downward through a common salt solution even when assisted by the portative effect of an electric current. As the resistance of the electrolyte to the passage of the electric current warms the electrolyte the chlorine. still less readily diffuses through the liquid. Therefore the task of keeping the ions separate is reduced to keeping the hydrate at the cathode from diffusing upward.

The experience of chemists and my experiment and observation show that neither the diaphragm nor the great specific gravity of caustic soda, nor the two in combination, can prevent the diffusion of caustic soda through the electrolyte.

To the influences already at work to keep the caustic soda in the lower zones of an electrolytic cell the process invented and herein described adds a third which effectually keeps the caustic soda within limits consistent with the continuous efficiency of the process. Though the superiority in weight of the caustic soda solution over the common salt solution is not a bar to upward diffusion of caustic soda, yet this difference in weight maybe utilized to cause a constant downward displacement of the caustic soda; and this downward movement of the mass is adjustable to the rate of upward difiusion of the caustic soda. The relative width of the zones Z and Z is preserved constant by means of continuous downward movement of the individual particles in solution. Following is a description of the method and means by which this adjustment is effected.

At some point in the chloride zone Z a solution of common salt, of the same strength as the original electrolyte is introduced. This has no tendency to flow upward and displace the liquid in the chlorine zone which is of the same specific gravity as the fresh electrolyte, nor to flow down through the soda which is heavier than the incoming salt solution. The downflow of the liquid in the zones Z and Z as a mass is caused by allowing caustic soda to flow out from the zone NA as the common salt solution is introduced into the zone Z The apparatus by which this adjustment of flow in mass to molecular diffusion is effected is shown in Figs. 1 and 2. A pipe P is introduced into the cell and extends horizontally across the compartment U immediately below the anode. In the upper side of the pipe P area number of apertures 10. It is preferable to have the pipe P extended and doubled or forked within the compartment U so that the apertures 19 may be distributed over a large area. P is the feed pipe which supplies the zone Z with fresh electrolyte in the manner indicated. The apertures 19 direct the incoming stream of electrolyte upon the lower limit of the chlorine zone. This stream,though so gentle in its flow as to leave the chlorine zone undisturbed, serves to keep the surface of the anode itself in contact with enough fresh electrolyte to maintain the process un interrupted. The supply of electrolyte is introduced to the pipe P by thefunnel at its outer end.

The pipe P, with its upward directing apertures, is adapted to the performance of two functions. The anode is constantly washed by fresh electrolyte from the apertures 19, and the electrolyte zone is kept supplied. The arrangement shown enables those two offices to be filled by one pipe P. Obviously, the apparatus may be divided according to functions and two supply pipes used, one to keep the anode in good contact with electrolyte, another to introduce the displacing liquid. The location and character of this supply pipe may vary with the solutions treated by my process. The principal feature of this process is the adjustment of flow in mass to progressive diffusion in an electrolytic column. The supply pipe P is the source of the flow in mass, and is to be located and constructed with a view to the peculiarities of the diffusion or diifusions to be offset, and also with reference to the relative densities of successive strata of liquid in the column. For instance, if only one of the ions is soluble and diffusive, the location of the supply pipe may be chosen with reference only to diffusion from one electrode toward the other. If both ions are soluble and diffusive the supply of electrolyte should be introduced to a middle ground between the electrodes,so that a flow in both directions offsets the two diffusions.

In the electrolysis of common salt solution, if the electrolyte be warm, so little chlorine is retained in solution that the supply of electrolyte may be introduced anywhere in the cell, so long as the displacement flow be adjusted to oppose the diffusion of caustic soda from the cathode, and the anode be kept in contact From the concentrated with fresh electrolyte. The above described location of the feed pipe P, withits apertures directed towardthe anode has proved a good arrangement for purposes of the process, although under proper conditions of tempera ture the outlet of pipe P may beplaced even above theanode, for thereasonsj ust expressed. Another mode of supplying the upper zone with sodium chloride is to suspend a basket of porous material in the electrolyte, filled with crystals of common salt. By percolation through the basket salt is supplied to the solution near the anode. This of course has no effect on the downward displacement of the lower zones, and merely serves as an auxiliary precaution for keeping the anode in good contact with fresh electrolyte. A tube T connects the lower portion of the zone Z with the caustic soda zone NA under the diaphragm. The tube T lies in the lowest portion of the compartment U and nearly the entire length of that compartment. soda zone NA at the end of the compartment L most remote from the lower end of the tube T (Fig. 1) passes the tube no. This tube rises to a height corresponding to the desired level of the electrolyte in the compartment U, when it turns in a siphon shaped delivery pipe. It is now obvious from the inter-communication of the liquid above and below the diaphragm that as fast as a solution of common salt flows into the cell through the apertures 19 so fast will a concentrated solution of caustic soda flow from the delivery end of the tube nain order to preserve the static balance of the liquids standing in the electrolytic cell and in the tube act.

Observation of the behavior of an electrolytic cell like the one described will enable an operator so to adjust the quantity of infiow'of electrolyte at P that the rate. of diffusion of caustic soda will be exactly balanced by the rate of supply of electrolyte.

Observation of an apparatus in continuous operation has determined the rate of flowneoessary to' balance exactly the upward diffusion of caustic soda. This is a general downward movement of from ten to twelve inches in twenty-four hours. The liquid between the electrodes is changed by this movement about once in six hours. The rate of flow depends on the circumstances under which the manufacturer labors. If a plentiful supply of sodium chloride solution is at hand, and chlorine is the product desired, the How through the cell may be rapid. The efficiency of the electric current under these conditions is nearly perfect. If on the other hand power is plentiful and. the double product is desired the flow in the cell may be reduced below the rate indicated above, and the distance between the electrodes increased, and highly concentrated caustic soda obtained with a loss of electric energy.

The above describedprocess of downward displacement includes within it a sub-process extends throughout by which a progressive concentration of the ion in solution below the diaphragm 1s effected. That portion of the electrolytic apparatus having for its function the progressive concentration of caustic soda consists of the tube T and the cathode B, (Figs. 1 and 2) constructed and arranged as follows: The tube T through which caustic soda is transferred from the diffused zone Z to the lower zone NA extends throughout nearly the whole length of the compartmentU,(Fig. 1) andliesat its lowermost portion where theinclined sides of the diaphragmD converge. The compartment L is divided transversely by a number of vertical partitions F affixed to or integral with the cathode base B. The partitions F conform to the desired shape and inclination of the diaphragm D which is supported by the partitions F at intervals throughout its length. The cells included between the partitions F communicate with one another through apertures which collectively form a central alley, a. The partitions F are at intervals extended up into the chamber H. These extensions are at as 00 (Figs. 1, 2 and 2 The transfer tube T enters the end cell marked 1; the soda delivery pipena emerges from the end cell marked 2. In the process of displacement already described diffuse caustic soda enters the alley near the cell 1 and passes in slow current through the cells to the cell 2. Meanwhile fresh caustic soda is being developed on the surface of the cathode B, so that in its flow from celll to cell 2 the caustic soda receives a succession ofincrements of concentration and is withdrawn from that portion of the apparatus where soda is most highly concentrated. That end of the tube T where difiuse soda enters it should be placed, if possible, at or near that portion of the diaphragm under which lies the cell containing the most concentrated soda. At that point the soda coming through the diaphragm will be densest and the tube T will withdraw from the zone Z the most concentrated caustic soda present in solution above the diaphragm.

The location of the tubeTof Fig. 1, causes a flow of diffuse soda from all parts of the compartment U toward the entrance of the tube T. The flow in U is parallel to the flow in L, so that as these parallel currents progress the liquid above and below the diaphragm increases in concentration. Thus the diffusive tendency is maintained nearly uniform along the entire length of the diaphragm'.

To carry on a process of progressive concentration, like that described above, it has been found advisable always to employ a succession of cells similar to those which divide the compartment L of Fig. 1, for otherwise the ebullition of the gases of electrochemical composition will stir the solution so that it will remain uniformly concentrated throughout. The employment of cellular construction confines this stirring to small spaces so that the general progression of concentration is not interrupted. This sub-process of progressive concentration may well be valuable in itself, and be em ployed'in electrolytic vessels wherein no diaphragm is used.

To avoid polarization by accumulation of gases at the electrodes of the apparatus the electrodesthemselves are made large and of irregular surface. The cathode B extends over the entire base of the apparatus, and inclines upward from its middle to two sides,

(Fig. 2) or toward its center (Fig. 4) accord-.

ing to the location and shape of the chamber H; The desired irregularity in surface is secured by making the partitions F of the same material as the base B. The partitions F thus form a series of deep corrugations upon the base B. Hydrogen liberated at such an electrode easily disengages itself from the surface and offersno impediment to the progress of the process.

The anode of this apparatus should be constructed, not only with a view to avoiding polarization, but also to meet other requirements peculiar especially to processes of electrolyses of chlorides. Like the cathode, the anode should have a large surface to avoid polarization, and further, it should be of such material as to resist the action of chlorine which, especially in its nascent state, attacks many substances'with avidity.

Of all known substances platinum fulfills the second requirement most completely; but if the electrolytic cell is large, a platinum anode extensive enough to escape polarization will be very costly. Gas carbon is cheap, resists the action of chlorine and may be used successfully as material for an anode if kept in good electric connection with the leading wires. Under the influence of an electric current gas carbon slowly wastes away; un-

less provision is made for this the contactwith the leading wires is liable to be broken and the current impeded or stopped. Gas

carbon slabs cast in.a lead plate have been used heretofore for electrodes; but in an apparatus where chlorine is present the contact between carbon and lead is soon broken by the formation of lead chloride in the joints between lead and carbon. gas carbon and almost any available metal, except platinum, will be interfered with by the action of chlorine in the same way. Gas carbon is hard and diflicult to cut into any regular form, so that where it may be used in rough lumps much expense is saved.

The electrode invented for use in connection with this process and apparatus overcomes the difficulties enumerated.

At the level in the electrolytic cell where the anode is to be secured a few platinum wires W are stretched across the cell. These wires are connected with the leading wires of the apparatus which lead to the contact.

Upon these wires lumps of gas carbon G are laid. The weight of these carbon lumps keeps them in good electrical contact with each other and with the supporting wires W.

Contact between The surface of the electrode thus constructed is, even in a small apparatus, whose cell 1S only four or five inches in diameter, many square inches in extent, so that the resistance due to polarization is reduced to a minimum. As the electric current wastes away the carbon lumps, they settle on the wires and on each other. The contact cannot be broken, and the'distance between anode and cathode is preserved constant. The leading wires of such an anode must be large to be of low resistance. A platinum leading wire of suitable size would be extremely costly; a leading wire used as a substitute for a platinum connection is constructed as follows: a large copper wire 0 (FigjLis incased in a close fitting lead tube L, which in turn is enveloped in a hard rubber jacket, B. At intervals along this insulated cable platinum pegs or screws P are driven through rubber and lead to the copper. The platinum supporting wires W, may be fastened to these pegs. Hard rubber is practically unaffected by chlorine; and lead only slightly. The chance of any chlorine-laden solution penetrating to the copper wire is therefore very small.

The only objection to the use of gas carbon is the discoloration of the liquids in the cell consequent upon the presence of small organic particles which drop from the carbon and come in contact with caustic soda. This circumstance is trivial in most cases, and does not affect-many commercial uses of canstic soda. If a clear liquid is desired, platinum anodes may be used. In place of carbon lumps, magnetite serves well, as will any mineral conductor not susceptible to the attacksof chlorine.

A form of electrolytic apparatus designed especially with a view to mechanical convenience is shown in assemblage and detail in Figs. 4c, 5, 6, 7, S, and 9. In this apparatus the various parts are grouped and attached so that all connections are made through and to the cathode-base.

Fig. 4 shows a cylindrical electrolytic apparatus, in vertical section. In it the relative location of the anode composed of carbons G, and platinum wires W, of the feed pipe P with its apertures p, the diaphragm D inclined toward a gas-chamber H, the cathode B, and the horizontal zones Z, Z Z and NA, is the same as in the apparatus of Figs. 1 and 2.

In the apparatus of Figs. t and 5, the hydrogen chamber H is internal instead of external, the leading'wire O, with its insulating jacket, andthe pipe P, are curved to conform in the cylindrical shape of the apparatus. The diaphragm D, in conformity to the shape of the apparatus, is conical, and rises to the middle of the apparatus,whereit delivers gases to the chamber H. Into the chamber 11 rises a continuation of the cathode-base, which may be integral therewith, or another piece ofthe same material as the cathode. This extension is shown in Figs. 4, 4&5 and 9 as containing radial cell walls 00', which correspond 1n function with the partitions w of Figs. 1, 2, and 2 So also the cathode B is composed of radial cells, intercommunicating through apertures in the partitions. These apertures collectively form a winding alley correspondlng in function with the straight alley a, of Fig. 2. The bell H and its inclosed partitions are of any suitable non corrodible material. The inclosed cylindrical cell 00 is preferably of the same material as the electrode on which it rests and of which it forms a continuation. The transfer tube T of this cylindrical apparatus 1s a short internal trap-tube T, shown 1n detail in Fig. 7, Fig.8) where there is provided a substitute for the trap-band of the tube in the shape of a plate or cup of inert material such as porcelaw or glass, situated immediately belowthe tube T. This is shown at 5, in Fig. 8. In the tube T of Figs. 1 and 7, and on the cup 5 of Fig. 8, no gases are developed, and none pass through the passage T into the upper chamber of the apparatus. The cell-wall nearest the passage T and'its gas-trap 5, contalns no aperture. On the other side of this blank Wallis the outlet pipe mt. For the diffuse soda to pass from T to ow, it is necessary for it to traverse the entire surface of the cathode by going around the circumference through the radial partitions. Thus the progressive concentration of soda is effected. The chief difference in construction (apart from general form) in this apparatus as distinguished from the rectangular one, is that all the connections, for admission of electricity or electrolyte and for withdrawal of products, are through the cathode base B. The bell b which forms the walls of the compartment U can be removed from the apparatus whose condition may be examined with a view to repairs or cleaning without necessitating the uncoupling of complicated connecting pipes and wires. Furthermore, the bell Z), may be of glass, and in one piece, so that leakage is impossible, and observation of the process possible at all times.

Fig. 5 shows the radial cells in place, the concentric arrangement of the leading wire and supplypipe, and the manner of stringing the supporting wires W.

Fig. 6 is a perspective view of the cellular cathode, without the central group of cells which extends up into the chamber H. This central group is preferably made in a separate piece, and is shown in Fig. 9.

Experience with various forms of apparatus involving the principles herein described has shown that for usual purposes the electrolysis in a single cell occasions a fall in electric pressure of about five volts. Ordinarily, electric current is furnishedat pressures much greater than five volts, so that to employ electro-chemical cells in parallel electric connection would result in enormous waste in. the generation of electricity, and would involve great expcnsein providing conductors of sufor a direct passage (as in.

ficient size and suitable construction. It will be found necessary in most instances, to multiply the number of electro-chemical cells in proportion to the electric pressure supplied, and to connect them in series.

Fig. 10 shows a battery of electrolytic cells connected in electric series, with accessory apparatus.

The nature of the electro-chemical process to be carried on renders necessary a substantially continuous supply of sodium chloride. This supply should be of uniform concentra' tion in all the cells of a battery and should for convenience be drawn from one common source. But, were unbroken streams of electrolyte to flow from this common source to all the cells, short-circuiting oi the electric current through the liquid would result, involvin gan appreciable loss of electric energy. To. avoid tl1is,and at the same time to secure the regular supply of electrolyte necessary to smooth continuity of the process, provision is made for a regularly intermittent supply of electrolyte, in uniformly measured portions furnished in broken streams from the common source of supply. In Fig. 1 there is shown in detail a contrivance for eifecting this purpose.

On a shaft M, is secured a tubular arm N open at both ends, bent so that part of its length lies along the sh aft M, then bent so as to extend out at right angles to the shaft, gradually bending from a radial to a circumferential direction so as to form a sickle-shaped scoop. As .theshaft M revolves this radial scoop N turns in the direction indicated by the arrow. The sector-part of the scoop Ndips beneath the surface of the electrolyte supply in the tank Y, situated under the shaft M. This supply is'ke'pt at constant level by a float valve Q (Fig. 10). The funnel E, leading to the supply pipe P, is placed under the shaft-outlet of the scoop tube N; as the shaft M revolves, the open scoop-tube spills the solution dipped up by its sector-part into the funnel E leading to the pipe P. This contrivance is multiplied to correspond with the number of cells in the battery, as illustrated in Fig. 10. By this means short-circuiting through the supply-tank is prevented, and an invariable supply of electrolyte secured. The level of sup ply in the tank Y is regulated by the ball valve Q. in Fig. 10. Similar precautions should be taken with the delivery tubes out; were a number of them to dipinto a common trough or tank, short-circuiting would result. The product of electrolysis should be made to drip intermittently from the tubes not. Should the flow be so copious as to deliver unbroken streams instead of successive drops, the endsof the tubes 'nct may be dipped in petroleum oil V floating on the surface of the main discharge pipe X, Fig. 1. Drops of cans- Jtic soda emerging from the tubes mt into petroleum oil will be much larger than drops formed in air. Petroleum oil does not offer sufficient conductivity to permit short-cirduced.

" ing products.

cuiting of the battery of cells, and serves the further purpose of keeping the outcoming caustic soda from contact with the air and the carbonic dioxide present in the air.

In Fig. 10, the chlorine pipes c are shown as led to a main pipe which conducts the chlorine to a chamber filled with unslaked lime, where bleaching powder may be pro- The hydrogen is collected in a gasholder to be used as fuel or as an illuminating agent Caustic soda is withdrawn to an evaporator, where the small amount of sodium chloride still in solution is crystallized out. The sodium chloride remaining after a slight evaporation of the solution will amount to no more than five per cent. of the aggregate Weight of sodium chloride and sodium hydrate in solution.

The above described displacement process of electrolysis when supplied to the decomposition of a solution of common salt results only in a downward displacement of gravitat- The displacement method is applicable to the treatment of substances of various specific gravity in such a way as to cause upward flow, as well as downward flow, or both simultaneously. To illustrate the adaptability of the process invented to displacement upward and downward in an electrolytic cell there is given the following description of method of and apparatus forelectro-chemically decomposing a solution of sodium sulphate. The electric current separates sodium sulphate into the elements sodium, sulphion and oxygen. The separation is represented as follows:

The sodiumat the cathode immediately forms sodium hydrate with the water in solution and liberates hydrogen. At the anode sulphion with the water in solution forms dilute sulphuric acid which being lighter than solution of sodium sulphate rises to the top of the elec trolytic cell and collects above the anode. Symbolically represented these attendant reactions are as follows:

Na +water:2(NAO H) +2H SO +water:H SO

So that here, as in the electrolysis of common salt, the elementary ions immediately form new combinations which are the ions practically available.

Fig. 11 represents an apparatus for electrolysis of sodium sulphate. This apparatus does not differ in principle of construction from the one shown in Figs. 1 and 2, except for the internal arrangement of the chamber H, and the absence of the cells in the cathode. The diaphragm D separates the cell into an upper compartment U and a lower compartment L. The inclined surface of the diaphragm D guides hydrogen liberated at the cathode into a chamber H whence it is conducted through a tube h. The iron cathode B and the platinum anode W with its gascarbons, occupy the same relative situation in the apparatus of Fig. 11, as do the electrodes of Figs. 1 and 2. A tube T communicates between the chambers U and L, a pipe not forms an outlet from the compartment L. A feed pipe P enters the cell between the electrodes and is similar in construction to the pipe P of Figs. 1 and 2. Upon the application of the electric current and the consequent formation of ions, the various substances in solution arrange themselves in the order of their specific gravity Under the diaphragm in the zone NA collects concentrated caustic soda. Immediately above the diaphragm there forms a zone Z of diffuse caustic soda. Between the zone Z and the anode WV lies the zone Z of undecomposed electrolyte sodium sulphate. Uppermost 1n the liquids isthc zone Z containingdilute sulphuric acid. Above the liquid in the cell oxygen collects in the space 0, to be drawn off through the tube 0. The reuniting of the ions in solution by diffusion is prevented in this apparatus by the inflow of fresh electrolyte through the pipe P. This pipe delivers the solution of sodium sulphate to the zone Z the incoming sodium sulphate displaces the sulphuric acid above it. The 9 acid is drawn off through the tube 1. The rise of the level of the liquids in the upper portion of the cell overbalances the sodium hydrate in the pipe no. so that the sodium hydrate is displaced downward and the sulphuric acid displaced upward by the entrance of sodium sulphate to the electrolytic cell at the zone Z The construction and operation of the apparatus and process herein described involve the operation of still another sub-process, by which the maintenance of gravimetrically disposed strata of liquid is materially assisted. The internal resistance of the electrolyte to the passage of an electric current heats the electrolyte, and this results in radiation of heat from the containing apparatus. By constructing the vessel as described, viz: with an iron base and sides of glass, slate or other inert material, the bottom of the vessel is rendered more conductive of heat than the upper portions. Thus the internal heat of the apparatus is conveyed away more freely from the lower strata than from the upper strata, and the resulting temperatures of the several portions of the contained liquid increase the already existing disparity in the specific gravities of the several strata. The more prominently this disparity is emphasized, the more successful will be the separation of the ion-containing strata. By lagging the sides of the upper part of the apparatus, as at 8, Fig. 12, and by providing external corrugations 9 upon the base of the vessel, the disparity in the relative heat-conductivities may still further be increased. Other methods of increasing this disparity will readily occur to the operator.

1. An electrochemical process which con sists of displacing an ionlin solution in an of the ion being at a rate equal to or greater than the rate of diffusion of the ion from its electrode through the electrolyte toward the opposite electrode said displacement being in a direction substantially opposite to the direction of said diffusion.

3. An electro-chemical process which consists of displacing an ion of superior specific gravity by supplying the electrolyte to the electrolytic cell, and withdrawing the displaced ion from the electrolytic cell; such supply of the electrolyte and withdrawal of i the ion being at a rate corresponding substantially to the rate of diffusion of the ion through the electrolyte toward the opposite electrode.

4. An electro chemical process which consists in maintaining within vthe electrolytic cell a zone of undecomposed electrolyte interposed between the ions at the electrodes by supplying to such zone fresh quantities of the electrolyte, thereby displacing the ions toward appropriate electrodes, and by withdrawing from the electrolytic cell the ions thus displaced; the supply of the electrolyte and the withdrawal of the ion being made to proceed at such a rate as to maintain the zone of undecomposed electrolyte between the ions substantially constant in volume.

5. An electro chemical process for producing sodium hydrate and chlorine from a solution of sodium chloride which consists of maintaining within the electrolytic cell a zone I of undecomposed solution of sodium chloride interposed between the sodium hydrate and chlorine at their respective electrodes by supplying to such zone fresh quantities of sodium chloride solution so as to displace the sodium hydrate toward its appropriate electrode and by Withdrawing from the'cell the sodium hydrate thus displaced; the supply 'of sodium chloride solution and the withdrawal of sodium hydrate being made to proceed at such a rate as to maintain the zone of undecomposed sodium chloride between theions substantially constant in volume.

6. A process of progressive concentration of i an ion in solution in an electrolytic cell, which consists of conducting the ion from that region in the electrolytic cell where it is difiuse; and passing it across the surface of the electrode where theion is being liberated, thus giving the difiuse ion, in its passage, successive increments of concentration from the electrode, and withdrawing from the electrolytic cell the ion thus laden with increments of concentration afterits passage across the electrode.

7. Aprocess of progressive concentration of an ion, which consists of displacing the diffused ion by introducing fresh electrolyte to that region into which the ion tends to diffuse, conducting the difiused ion thus displaced from that point in the said region where it is most concentrated to the electrode at which the ion originates, and there passing the ion across the surface of the said electrode where constant increments of concentration are being supplied, and finally discharging the ion laden with increments of concentration after its passage across the electrode.

- 8. Aprocess of progressive concentration of the solution of sodium hydrate obtained from electrolysis of a solution of sodium chloride which consists in displacing the dilfused sodium hydrate by introducing a supply of sodium chloride into that region in the electrolytic cell into which sodium hydrate tends to diffuse from the cathode, conducting the diffused sodium hydrate thus displaced by the fresh supply of sodium chloride from the point in the said region where the sodium hydrate is most concentrated to the cathode where ing the difiused sodium hydrate across the surface of the cathode, whereconstant increments of sodium hydrate are added to the solution, and discharging the sodium hydrate solution after it has received increments of concentration in its passageacross the cathode.

9. An electrolytic apparatus containing in combination with horizontal electrodes, a diaphragm located between the electrodes and separating the electrolytic cell into compartments, a supply inlet to one compartment, a passage between the compartments, and a discharge outlet from the other compartment, substantially as and for the purpose described. i i

10. In an electrolytic apparatus the combination of electrodes situated in diaphragm separated compartments, a supply inlet to one compartment,adischargeoutlet fromtheother compartment, and a passage between the compartments, substantially as and for the purpose set forth.

11. In an electrolytic apparatus the combination of electrodes situated in diaphragm separated compartments, a supply inlet to one compartment, a discharge outlet from the other compartment, a passage between the compartments anda gas-chamber, so situated as to receive the gases rising in the lower comsodium hydrate originates, and there pass- IIO partment, substantially as and for the purpose set forth.

12. In an electrolytic apparatus, the combination of compartments separated by a porous diaphragm, a gravity contact electrode situated in one compartment, a supply pipe for electrolyte, entering the apparatus on one side of the diaphragm, a discharge pipe from the apparatus on the other side of the diaphragm,a passage between the compartments, and a gas chamber, so situated as to receive the gases rising in the lower compartment, substantially as and for the purpose set forth.

13. In an electrolytic apparatus, the combination of compartments separated by a porous silicious diaphragm, an electrode of carbon in gravity contact with platinum wires situated in one compartment, a supply pipe for electrolyte on one side of the diaphragm, a discharge pipe on the other side of the diaphragm, a passage between the compartments and a gas chamber, so situated as to receive the gases rising in the lower compartment, substantially as and for the purpose set forth.

14. In an electrolytic apparatus, the combination of an inclined diaphragm supported by a corrugated electrode, and a gas-chamber at the uppermost part of the inclineddiaphragm, substantially as and for the purposes set forth.

15. In an electrolytic apparatus, the co mbination of a concavo-convex porous diaphragm supported by a corrugated electrode and a gas-chamber, situated at the highest point in the diaphragm, substantially as and for the purposes set forth.

16. In an electrolytic apparatus, an electrode containing a series of connecting chambers, a supply inlet to one end of the series, and a discharge outlet from the other. end thereof, substantially as described.

17. The combination in a containing vessel composed of separable parts, of electrodes, leading wires, a supply pipe for electrolyte, and outlets for electrolytic products all of whose connections are made through one of the separable parts of the containing vessel, substantially as and for the purpose set forth.

18. The combination,ina containing vessel having a separable base of electrodes, leading wires, a supply pipe for electrolyte, and outlets for products of electrolysis, all of whose connections pass through the separable base, substantially as and for the purpose set forth.

19. An electrolytic apparatuswhose cathode is the base of the apparatus, and in which the leading wire of the anode, the supply pipe for electrolyte and the discharge pipes for the products of the electrolysis pass through the cathode-base, substantially as described.

20. In an electrolytic apparatus the combination of electrodes, diaphragm separated compartments and aconduit from one compartment to the other provided with a gastrap,substantially as and for the purpose set forth.

21. In' an electrolytic apparatus, a containing case, electrodes situated in diaphragm separated compartments, the diaphragm, a passage between the compartments, a supply inlet to one compartment, a series of connecting chambers in the other compartment, a supply inlet for said series arranged at one end thereof, and a discharge outlet for said compartment and series located at the other end of the series, substantially as described.

22. An electrode which consists of two systems; first, an internal system of corrodible conductors surrounded and insulated by noncorrodible material; second, an external sys tem of uninsulated, non-corrodible conductors, the internal and external systems being connected electrically by non-corrodible metallic pins, which pass through the insulation of the internal system in such manner as to exclude all corrosive agents from the internal system while maintaining and preserving good electrical contact with the external system.

23. A leading-in wire composed of a copper conductor enveloped in a rubber jacket, and

'platinu m-pins which pass through the rubber jacket to the copper, establishing electric contact with the latter, the ends of the platinum pins which project out of the rubber being adapted to the attachment of electrical connections with an electrode.

24. The combination with an leading-in Wire, of metallic conductors which pierce the insulation and make contact with the leading-in wire, and an electrode consisting of non-metallic conducting pieces in gravity contact with metallic conductors, the latter attached to the metallic conducting points, which pierce the insulation of the leading-in WIIG.

25. The method of constructing a porous diaphragm, which consists in filling a reinforcing framework with Portland or analogous cement, and molding the framework thus filled, while plastic, into the shape desired.

26. A diaphragm of porous Portland or analogous cement, reinforced by fibrous or textile material, the fibrous or textile material being filled and protected by the cement.

27. A diaphragm of porous Portland or analogous cement, reinforced by asbestus fibers, substantially as herein described.

28. The method of increasing the disparity of the specific gravities of. gravimetrically disposed strata in an electrolyte, which coninsulated sists in maintaining the upper strata'at a temperature higher than the lower'strata, meanwhile preserving the said strata from agitation and disarrangement of their gravimetric distribution.

29. The method of increasing the disparity of the specific gravities of gravimetrically disposed strata in an electrolyte, which consists of permitting the heat of the electrolyte to radiate more freely from the lower strata than from the upper strata, meanwhile preserving the said strata from agitation and name to this specification in the presence of disarrangement of their gravimetric distritwo subscribing witnesses. 1 bution.

30. In an electrolytic apparatus, a metal- HENRY GARMIOHAEL' 5 H0, corrugated base, and sides of non-heat Witnesses:

conducting material. FREDERICK L. EMERY,

In testimony whereof I have signed my ELEANOR F. GROLL. 

